1. Field of the Invention
The present invention relates to a method and apparatus for performing trick play, and more particularly, to a method and apparatus for performing trick play on an input scrambled transport stream.
2. Description of the Related Art
In general, scrambled data streams are input to digital televisions (TVs) that can process moving picture experts group 2 (MPEG2) and H.264 data streams. In particular, European digital TVs are required to store scrambled data streams that are stored without being descrambled.
FIG. 1 illustrates a conventional personal video recorder (PVR) system 100 for performing trick play on a scrambled audio/video (AV) stream 120.
Referring to FIG. 1, the conventional PVR system 100 includes a transport stream (TS) demultiplexer 112, a TS de-scrambler 114, a TS rescrambler 116, and an MPEG2 decoder 118.
A conventional method of performing trick play on the scrambled AV stream 120 by using the conventional PVR system 100 will now be explained. The TS demultiplexer 112 receives the transmitted AV stream 120 and demultiplexes a program therefrom. The TS descrambler 114 descrambles the AV stream 120 and the TS rescrambler 116 stores an original data stream in a storage device 110. Sequence header information, Intra (I) picture information, predicted (P) picture information, and bi-directional (B) picture information (or sequence parameter set information, instantaneous decoding refresh (IDR) picture information, and non-IDR picture information) which are extracted from metadata of the descrambled AV stream 120 are also stored together with the original data stream in the storage device 110.
The MPEG2 decoder 118 decodes and reproduces a picture selected by using the sequence header information, the I picture information, the P picture information, and the B picture information (or the sequence parameter set information, the IDR picture information, and the non-IDR picture information).
However, the conventional method described with reference to FIG. 1 can be used only when both sequence header position information and picture position information can be known in advance. Accordingly, the conventional method cannot perform trick play when a scrambled stream is to be stored without being descrambled because picture position information cannot be known in advance.